Sand Dunes Reading Answers

Nov 30, 2022

Sand Dunes Reading Answers contains 14 questions which need to be answered in 20 minutes. Sand Dunes Reading Answers consists of two types of questions; matching the paragraphs and choose the correct option. Candidates need to skim the passage for keywords, understand the concept and answer based on the given instructions.In choose the correct option, candidates are required to answer based on a given cue. For matching the heading, candidates are required to match the given options with the paragraphs presented in the paragraph. Candidates must read the IELTS reading passage, identify keywords, and recognize synonyms to answer the question.

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Reading Passage Questions

One of the main problems posed by sand dunes is their encroachment on human habitats. Sand dunes move by different means, all of them aided by the wind. Sand dunes threaten buildings and crops in Africa, the Middle East, and China. Preventing sand dunes from overwhelming cities and agricultural areas has become a priority for the United Nations Environment Program. On the other hand, dune habitats provide niches for highly specialized plants and animals, including numerous rare and endangered species.
Sand is usually composed of hard minerals such as quartz that cannot be broken down into silt or clay. Yellow, brown and reddish shades of sand indicate their presence of iron compounds. Red sand is composed of quartz coated by a layer of iron oxide. White sands are nearly pure gypsum. Sand with a high percentage of silicate can be used in glassmaking. Sandstone is created by sand, mixed with lime, chalk or some other material that acts as a binding agent, that is deposited in layers at the bottom of a sea or other area and pressed together into rock by the great pressure of sediments that are deposited on top of it over thousands or millions of years.
The most common dune form on Earth and on Mars is crescentic. Crescent-shaped mounds are generally wider than they are long. The slipfaces are on the concave sides of the dunes. These dunes form under winds that blow consistently from one direction, and they also are known as barchans or transverse dunes. Some types of crescentic dunes move more quickly over desert surfaces than any other type of dune. A group of dunes moved more than 100 metres per year between 1954 and 1959 the China’s Ningxia Province, and similar speeds have been recorded in the Western Desert of Egypt. The largest crescentic dunes on Earth, with mean crest-to-crest widths of more than 3 kilometres, are in China’s Taklamakan Desert.
Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on there or more arms that radiate from the high center of the mound. They tend to accumulate in areas with multidirectional wind regimes. Star dunes grow upward rather than laterally. They dominate the Grand Erg Oriental of the Sahara. In other deserts, they occur around the margins of the sand seas, particularly near topographic barriers. In the southeast Badain Jaran Desert of China, the star dunes are up to 500 metres tall and may be the tallest dunes on Earth. Straight or slightly sinuous sand ridges typically much longer than they are wide are known as linear dunes. They may be more than 160 kilometres (99 mi) long. Some linear dunes merge to form Y-shaped compound dunes. Many forms in bidirectional wind regimes. The long axes of these dunes extend in the resultant direction of sand movement. Linear loess hills known as pahas are superficially similar.
Once sand begins to pile up, ripples and dunes can form. Wind continues to move sand up to the top of the pile until the pile is so steep that it collapses under its own weight. The collapsing sand comes to rest when it reaches just the right steepness to keep the dune stable. This angle, usually about 30-34°, is called the angle of repose. Every pile of loose particles has a unique angle of repose, depending upon the properties of the material it’s made of, such as the grain size and roundness. Ripples grow into dunes with the increase of wind and sand input.
The repeating cycle of sand inching up the windward side to the dune crest, then slipping down the dune’s slip face allows the dune to inch forward, migrating in the direction the wind blows. As you might guess, all of this climbing then slipping leaves its mark on the internal structure of the dune. The image on the right shows fossil sand dune structure preserved in the Merced Formation at Fort Funston, Golden Gate National Recreation Area. The sloping lines or laminations you see are the preserved slip faces of a migrating sand dune. This structure is called cross-bedding and can be the result of either wind or water currents. The larger the cross-bedded structure, however, the more likely it is to be formed by wind, rather than water.
Sand dunes can “sing” at a level up to 115 decibels and generate sounds in different notes. The dunes at Sand Mountain n Nevada usually sing in a low C but can also sing in B and C sharp. The La Mar de Dunas in Chile hum in F while those at the Ghord Lahmar in Morocco howl in G sharp. The sounds are produced by avalanches of sand generated by blowing winds. For a while, it was thought that the avalanches caused the entire dune to resonate like a flute or violin but if that were true then different size dunes would produce different notes. In the mid 2000s, American, French and Moroccan scientists visiting sand dunes in Morocco, Chile, China and Oman published a paper in the Physical Review Letters that determined the sounds were produced by collisions between grains of sand that caused the motions of the grains to become synchronized, causing the outer layer of a dune to vibrate like the cone of a loudspeaker, producing sound. The tone of the sounds depended primarily on the size of the grains.
Scientists performed a computer simulation on patterns and dynamics of desert dunes in laboratory. Dune patterns observed in deserts were reproduced. From the initial random state, stars and linear dunes are produced, depending on the variability of the wind direction. The efficiency in sand transport is calculated through the course of development. Scientists found that the sand transport is the most efficient in the linear transverse dune. The efficiency in sand transport always increased through the evolution, and the way it increases was stepwise. They also found that the shadow zone, the region where the sand wastes the chance to move, shrinks through the course of evolution, which greatly helps them build a model to simulate a sand move.

Solution and Explanation
Question 1-8:
Choose the correct heading for paragraphs A-H from the list below.
Write the correct number, i-x, in boxes 1-8 on your answer sheet.

List of Headings

i potential threat to buildings and crops despite of benefit.
ii the cycle of sand moving forward with wind
iii protection method in various countries.
iv scientists simulate sand move and build model in lab
v sand composition explanation
vi singing sand dunes
vii other types of sand dunes
viii the personal opinion on related issues.
ix reasons why sand dunes form
x the most common sand type

Q1. Paragraph A

Answer: i- potential threat to buildings and crops despite of benefit.
Supporting statement: Preventing sand dunes from overwhelming cities and agricultural areas has become a priority for the United Nations Environment Program. .
Keywords: preventing sand dunes, provide niches
Keyword Location: para A, line 6
Explanation: There is a major problem faced due to the sand dunes as they overwhelm the cities and impose challenges for cultivated areas. It has in the long run turned out as a major complication for the United Nations Environment Program. However, it is beneficial to some like highly specialzed animals and plants.

Q2. Paragraph B

Answer: v- sand composition explanation
Supporting statement: Sand is usually composed of hard minerals such as quartz that cannot be broken down into silt or clay
Keywords: composed
Keyword Location: Para B, line 1
Explanation: This paragraph explains the composition of sand. According to the paragraph, sand is composed of quartz, iron compound, gypsum, silicate, and many other minerals.

Q3. Paragraph C

Answer: x- the most common sand type
Supporting statement: The most common dune form on Earth and on Mars is crescentic
Keywords: common
Keyword Location: Para C, line 1
Explanation: It has been portrayed that most common sand dunes are crescentic. These are mostly found on earth and the moon.

Q4. Paragraph D

Answer: vii- other types of sand dunes
Supporting statement: Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on there or more arms that radiate from the high center of the mound
Keywords: sand dunes
Keyword Location: para D line 1
Explanation: It has been stated in the paragraph that there are a variety of sand dunes. They are gradually symmetrical sand dunes and star sand dunes.

Q5. Paragraph E

Answer: ix- reasons why sand dunes form
Supporting statement: Once sand begins to pile up, ripples and dunes can form.
Keywords: dunes can form
Keyword Location: para E, line 1
Explanation: It has been portrayed in the reading passage that sand dunes are composed by the piling and ripple of the sand. WIth conitnuous blow of winds, the sand piles up and reaches a certain height, then the pile ripples due to its own weight. The sand falls and comes to rest until it reaches the right steepness to balance the dune. Thus dunes are formed.

Q6. Paragraph F

Answer: ii- the cycle of sand moving forward with wind
Supporting statement: The repeating cycle of sand inching up the windward side to the dune crest, then slipping down the dune’s slip face allows the dune to inch forward, migrating in the direction the wind blows
Keywords: migrate
Keyword Location: para F, line 3
Explanation: Blowing of constant of wind in a specific direction blows the sand in a way that it rises to an inch up to the dune crest. Furtehr, sand falls of to a certain level at the dune slip face and allows it to move an inch forward.

Q7. Paragraph G

Answer: vi- singing sand dunes
Supporting statement:Sand dunes can “sing” at a level up to 115 decibels and generate sounds in different notes
Keywords: sing
Keyword Location: para G, line 1
Explanation: As mentioned in the reading passage, the air which blows over the sand dunes causes collision of grains of the sand amongst each other. It leads to a vibrating sensation of sand dunes and produces a sound of 115 decibels.

Q8. Paragraph H

Answer: iv- scientists simulate sand move and build model in lab
Supporting statement: Scientists performed a computer simulation on patterns and dynamics of desert dunes in laboratory.
Keywords: scientists
Keyword Location: para H
Explanation: In the modern era, scientists perform computer simulations in patterns and forms of dynamics of desert dunes in the lab. Thus, they are able to create sand dunes in an artifical environment.

Questions 9-10:
Answer the questions 9-10 and choose correct letter A, B, C or D.

Q9. What is the main composition of white sand made of according to the passage?

Quartz
Gypsum
Lime
Iron

Answer: B- Gypsum
Supporting statement: White sands are nearly pure gypsum.
Keywords: gypsum
Keyword Location: para B, line 3
Explanation: It is conclusive from the paragraph that the major component of white sand is Gypsum.

Which one is not mentioned as a sand type in this passage?

Linear
Crescentic
Overlap
Star

Answer: C- Overlap
Supporting statement: Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on there or more arms that radiate from the high center of the mound. The most common dune form on Earth and on Mars is crescentic
Keywords: radially ,symmetrical ,crescentic,
Keyword Location: Para C&D, line 1
Explanation: There has been no mention of the type of overlapping sand dunes.

Questions 11-14:
Complete the summary using the list of words, A-J below.
Write the correct letter, A-J in boxes 11-14 on your answer sheet.

A quartz B shape C pressure
D tone E protection F category
G minerals H sing I lab
J direction

Crescentic is an ordinary 11 ____ on both Earth and Mars, apart from which, there are also other types of sand dunes. Different color of the sand reflects different components, some of them are rich in 12 ____ that can not be easily broken

into clay. Sand dunes can “sing” at a level up to 115 decibels and generate sounds in different notes. Sand dunes can be able to 13 ____ at a certain level of sound intensity, and the different size of grains creates different 14 ____ of the sound.

Question 11:

Answer: shape
Supporting statement: Crescent-shaped mounds are generally wider than they are long. Crescent shaped
Keywords: crescent
Keyword Location: para C line 1
Explanation: The Crescentic sand dunes are crescent-shaped mounds.

Question 12:

Answer: minerals
Supporting statement: Sand is usually composed of hard minerals such as quartz that cannot be broken down into silt or clay.
Keywords: minerals
Keyword Location: para B line 1
Explanation: According to the passage sand dunes are a composition of hard minerals which cannot be broken into silt or clay.

Question 13:

Answer: sing
Supporting statement: Sand dunes can “sing” at a level up to 115 decibels and generate sounds in different notes
Keywords: sing
Keyword Location: para G line 1
Explanation: It is conclusive from te reading passage that some sand dunes can sing upto a mark of 115 decibel. This generally happens due to the top solid layer of the sand dunes.

Question 14:

Answer: tone
Supporting statement: The tone of the sounds depended primarily on the size of the grains.
Keywords: tone
Keyword Location: para G, last line
Explanation: The size of the sand grains decide the tone pof the song. These sand grains must e located on the top layer of the sand dunes.

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